The present disclosure relates to a sheet package, and more particularly to a sheet package which protects with a package material the outside of stacked sheets and which sheet package can be set in a printing unit together with the package material; and to a printing unit to/from which the sheet package can be attached/detached.
In a conventionally known box-shaped package material, stacked sheets are stored. When the sheets are used for printing, by opening the lid of the package material, and by folding the lid back to the opposite side, the sheets are set in the printing unit together with the package material (see, for example, Japanese Patent Application Laid-Open No. 2003-285939). Ease of use of this sheet package is enhanced because a plurality of sheets can be handled as a package unit. Further, because the sheets on the inside are covered and thus protected, effectiveness has proved possible when heat sensitive papers weak to light or heat are stored as the sheets. Further, there has been known a printing unit in which the sheet package is loaded with sheets stored in a stacked condition and partially exposed from the sheet package, and in which printing unit sheets are pulled out from the sheet package and printed (see, for example, Japanese Patent Application Laid-Open No. 2003-176041). This kind of printing unit is provided with a contact portion with which one side end of the sheet package makes contact in a sheet package storage portion, and a sheet package-pressing means for pressing the other side end portion of the sheet package is provided on a side face on the opposite side of the storage portion, so that the one side end portion of the sheet package is pressed against the contact portion provided in the storage portion by means of pressing of the sheet package-pressing means.
However, according to the conventional sheet package described in the Japanese Patent Application Laid-Open No. 2003-176041, if the lid of the storage portion is closed in a condition in which the sheet package has not been properly loaded at the time that the sheet package was stored in the storage portion, a side end portion of the sheet package has sometimes tended to be caught between the lid and an outside portion of the storage portion on the side provided with the contact portion. In such cases, if the side end portion of the sheet package does not have sufficient strength, the sheet package is simply crushed, and the sheet package is accordingly not pushed into the storage portion by the pressing force of the lid.
If the kind of situation described above does occurs, even when sufficient sheets are stored, a sheet sensor cannot detect any sheet, and in consequence, despite the fact that sufficient sheets are stored the sensor tends to determine that all sheets have been used up, thereby making it impossible for printing to take place.